1. Field of the Invention
The invention relates to heat transfer and, more particularly, to heat transfer in a hand-held portable electronic device.
2. Brief Description of Prior Developments
Heat spreader elements are known which have been used for transferring heat from hot components. Materials such as copper, aluminum, silicon or graphite foil have been used for example. It is known to use a heat spreader encapsulated by using conventional thermoset (e.g. epoxy material).
A conventional method of cooling of a mobile device is based on use of a thermally high conductive printed wiring board (PWB). Heat is conducted from the integrated circuits (ICs) to the PWB; which is capable to spread the heat to the whole PWB area and, furthermore, to mechanics. High thermal conductivity of the PWB is achieved with using large, constant, and thick power and ground (GND) layers made of copper. This has been a sufficient method for cooling the low power devices so far. However, new technologies set totally new environment and requirements for cooling of mobile devices.
In mobile electronics, constantly increasing miniaturization with simultaneous increased need for higher power levels make thermal management of the device demanding due to the maximum temperatures for device surfaces and components. Efficient thermal management is one the elements enabling product functionality and increasing reliability. By enhancing cooling, higher power levels can be applied enabling added functionalities and performance. From a thermal point of view, there are a variety of cooling options to follow starting from chip level and package structural design to system level thermal management optimization. However, if focusing in conventional cooling solutions based on materials or cooling devices, they must be more and more integrated in the current mechanics due to miniaturization requirements.
In mechanics, most of the covers and chassis of mobile devices are currently made of thermoplastics using injection-molding technology. Thermoplastics, as such, are thermal insulators with their very low value of thermal conductivity. In practice, this prevents heat spreading in the mechanics causing localized high temperatures “hot spots”.
U.S. patent application Ser. No. 11/157,719, which is hereby incorporated by reference in its entirety, discloses one type of heat transfer system used in a mobile telephone. There is a desire to provide a new type of system for mobile devices, such as hand-held portable electronic devices, which have a different type of heat spreader system, and a method of manufacturing.